@article{LO05,
  author    = {Bas Luttik and Vincent van Oostrom},
  title     = {Decomposition orders---another generalisation of the fundamental theorem of arithmetic.},
  journal   = {Theor. Comput. Sci.},
  volume    = {335},
  number    = {2-3},
  year      = {2005},
  pages     = {147-186}
}